Rotary internal combustion engine



Dec. 26, 1967 c. GROTH I ROTARY INTERNAL COMBUSTION ENGINE Fil ed March 9, 1966 INVENTOR Y ELALIS ERDTH K PWze.

AGENT United States Patent N 6 Claims. (Cl. 123-8) This invention relates to internal combustion engines of the trochoidal type of construction, having an outer body comprising a multilobed peripheral housing having a basically epitrochoidal inner surface and a pair of parallel end Walls, and a multiapexed inner body disposed therein and rotatable about a rotor axis spaced from and parallel to the outer body longitudinal axis. The junctions of the outer body lobes form zones relatively close to the longitudinal axis, and ignition occurs in one of these restricted zones.

The end faces of the inner body or rotor bear end seals sliding in sealing relation against the end walls to seal the variable volume chambers formed between the rotor and the outer body. Such end face seals comprise striplike members, seated in grooves on each rotor end face generally parallel to the periphery of the rotor and spaced a minimal distance therefrom. At some rotor positions, and particularly at the ignition position, the rotor motion is such that the end face seal along one edge of the rotor is traveling substantially longitudinally, whereby it scores the contacting surface of the end wall in a knifelife manner in the ignition region. Such wear eventually erodes the surface of the end wall to such a degree that sealing in the ignition region is substantially diminished.

To remedy this disadvantage it has previously been proposed to plate or flame-spray the inner surfaces of the end walls with a material having high resistance to wear, such as chromium or molybdenum, for example. This procedure has the desired result but is too expensive for quantity production, owing to the high cost of such metals. Therefore, it has further been suggested to plate or spray with hard metal only those regions of the end walls particularly subject to this type of wear and where sealing loss is serious. With this solution it is necessary to provide,

.in those regions of the end walls to be covered with a sprayed layer, recesses in the end wall into which the hard metal can be deposited. With the subsequent shrinkage as the hot-sprayed metal cools, gaps may develop at the transition to the base material, and as the end seals sweep over such gaps the sprayed material tends to crumble.

The present invention overcomes such disadvantages of the prior art by providing the end walls with recesses into which the more expensive material with high wear resistance may be sprayed in the zones closer to the axis, or at least in the zone where ignition occurs, and the remainder of the wall recess filled with a cheaper metal in less critical areas, with a gradual overlapping transition to the highly resistant material, and good bonding between the two sprayed metals.

It is therefore an object of this invention to provide a rotary combustion engine in which scoring of the end walls by the rotor end face seals in critical zones is prevented.

Another object is to provide abrasion and wear-resistant inner surfaces at critical zones on the end walls of a rotary combustion engine.

A further object of the invention is to provide end walls for a rotary combustion engine, having surfaces exhibiting different wear resistance in different areas.

The foregoing objects and others ancillary thereto will be readily understood on reading the following specification in connection with the accompanying drawings, in which:

FIG. 1 is an elevation in cross-section along the longitudinal axis of an engine of the type described;

FIG. 2 is an elevational view of the inner surface of one of the end walls, taken on line 2-2 of FIG. 1; and

FIG. 3 is an interrupted elevational cross-section of the end wall taken on line 3-3 of FIG. 2.

In FIG. 1 there is shown a rotary internal combustion engine of the type described, having an outer body generally indicated at 11, comprising a peripheral housing 12 and a pair of axially spaced end walls 13 and 14. A shaft 16 transpierces the end walls along the longitudinal axis of the outer body, and has an eccentric portion 17 disposed therein on which is rotatably positioned an inner body or rotor 18, having the peripheral outline shown in dotted line in FIG. 2. The inner surface 19 of housing 12 has a basically epitrochoidal multilobed profile along which the rotor apexes sweep in sealing relation.

Each rotor apex bears a longitudinally disposed apex seal strip 21, and each end face of the rotor bears end face seals 22 disposed in grooves adjacent to the periphery of the rotor and generally parallel therewith. Intermediate seal bodies 23 are disposed in bores on each end face of the rotor at the apexes, and receive the ends of apex seals 21 and end face seals 22 to form a complete sealing systern for each of the variable volume chambers formed between the working faces of the rotor and the inner surface of the peripheral housing. The outer bodyis provided with appropriate intake and exhaust ports (not shown), and a spark plug 24 in the waist region of the peripheral housing, that is, the junction between the lobes of the epitrochoid.

FIG. 2 shows the inner surface of one end wall 13, with the approximate angular position of the spark plug 24 shown schematically, and the rotor 18 shown in dotted line in approximately the position it occupies at ignition. The epitrochoid outline 26 shown in dotted line is the path traced by the apex seals 21 sweeping the inner surface of the peripheral housing.

In the rotor position shown in FIG. 2 the end face seals parallel to the upper edge of the rotor are traveling substantially longitudinally. Such orientation of the end face seals with respect to their direction of travel occurs only at the zones where the lobes of the epitrochoid meet, and experience has shown that there is a tendency to wear and score the end walls in those zones. This wear is more serious in the ignition region, where it may result in some loss of compression and loss of combustion gases when ignition is initiated, reducing the efliciency of the engine.

In accordance with the invention, that portion 27 exposed to the greatest wear in the ignition region is provided with a coating of highly wear-resistant material, and the remaining portion 28 of the end wall which is exposed to the rotor is provided with a coating of cheaper, less wear-resistant material. If desired, the wear portion of the plate opposite to portion 27 may also be provided with wear-resistant coating, but this is less important in the intake-exhaust region, where the gas pressures are lower.

The method of applying the two components of the coating is best shown in FIG. 3, and is particularly adapted for use with lightweight engines in which the outer body is formed of aluminum or other relatively soft alloy. A recess 29 is milled or otherwise produced in the inner surface of the end plate; the recess may have the peripheral outline of the epitrochoid, or may have an outline parallel to the edge of the plate. It is necessary that it be large enough in area that its edge will be overlapped all around by the peripheral wall 12 when the engine is assembled. The exact depth of the recess is not critical, but

should be so chosen as to be deep enough to allow control of the metal spraying process and deposition of a substantial amount of material, but not deep enough to render it too costly to fill. The finished depth, after the plate has had its inner surface ground flat, maybe from about .005 to .015", with an optimum about .010".

Any suitable wear-resistant material may be used, such as molybdenum or chromium, of which molybdenum is preferred, not only because it withstands frictional abrasion very well, but also because it has a high degree of adhesion to any of the basemetals commonly used for such end plates. The entire bottomof recess 2 is sprayed with a thin coat of molten molybdenum to take advantage of this adherent characteristic, then area 27 is built up with molybdenum above the surface of the end plate and slightly overlapping the edge of the recess, as shown in dotted line in FIG. 3, with the heavier deposit sloping gently to the thin layer in the bottom of the recess. The remainder of the recess is then filled to above the surface with a cheaper metal 28, such as mild steel or bronze, sprayed on in the same manner. The steel or bronze adheres very well to the layer of molybdenum, and has a sloping junction therewith where the molybdenum comes to the surface. Lastly, the whole surface of the plate is ground flat, with a perfect transition between the two filler metals at the overlap.

Aluminum alloys or other lightweight alloys which may be used for the base metal of the end plate commonly have a much higher coefficient of thermal expansion than the materials with which the recess is filled. Consequently, either on cooling of the sprayed metal or during service in the engine, slight gaps may develop around the edge of the recess, as shown by the dotted lines 31 in FIG. 3. Since these gaps are covered by the edge of the peripheral wall 12, they are not exposed to a crumbling action by seal wear, and no sealing eificiency is lost by gas leakage through such gaps.

If by any combination of materials or process it is found that the softer sprayed metal has better adhesion to the base than the wear-resistant metal, the procedure of application may be reversed and the softer metal sprayed first into the recess, with an adhesive coat over the bottom.

Although the invention has been described above with reference to a preferred embodiment, various changes and modifications may be made by those skilled in the art without departing from the scope of the invention. It is intended to cover all such modifications by the appended claims.

What is claimed is:

1. A rotary internal combustion engine, comprising in A combination an outer body having a peripheral wall with a basically epitrochoidal multilobed inner surface and a pair of parallel end walls spaced apart by said peripheral wall along the longitudinal axis thereof; said peripheral wall having lobe junctions in a Zone closer to said longitudinal axis than the remainder of said wall; a drive shaft transpiercing said end walls and having an eccentric portion disposed within said outer body, said eccentric portion having an axis displaced from and parallel to said outer body axis and planetating therearound; a multiapexed inner body disposed within said outer body and mounted on said eccentric portion for rotation about said eccentric axis with said apexes sweeping said inner surface in sea-ling relation thereto; said inner body having at each end thereof an end face bearing end face seals disposed adjacent to the edges of said end face and generally parallel thereto, said end face seals sweeping the inner surface of said end walls in sealing relation thereto; each of said end walls having its inner surface faced with a hard Wear-resistant metal in the region of at least one of said lobe junctions and the remainder of the inner surface faced with a less wear-resistant metal.

2. The combination recited in claim 1, wherein ignition takes place in the region of one of said lobe junctions,

and said wear-resistant facing is in said ignition region.

3. The combination recited in claim 2, wherein said hard wear-resistant metal is selected from the group consisting of molybdenum and chromium, and said less wearresistant metal is selected from the group consisting of mild steel and bronze.

4. The combination recited in claim 3, wherein said selected wear-resistant metal is molybdenum, and said. selected less wear-resistant metal is mild steel.

5. The combination recited in claim 4, wherein each of said end wall inner surfaces has a recess therein, said molybdenum is deposited in said recess thick enough in said ignition region to leave an exposed molybdenum surface and thinly in the remainder of said recess, and the remainder of said recess is filled with said mild steel.

6. The combination recited in claim 5, wherein said recesses are of larger dimension than the profile of said peripheral wall inner surface, and the edges of said recesses are covered by the ends of said peripheral wall.

References Cited UNITED STATES PATENTS 3,289,649 12/1966 Lamm 123 s RALPH D. BLAKESLEE, Primary Examiner. 

1. A ROTARY INTERNAL COMBUSTION ENGINE, COMPRISING IN COMBINATION AN OUTER BODY HAVING A PERIPHERAL WALL WITH A BASICALLY EPITROCHOIDAL MULTIOBED INNER SURFACE AND A PAIR OF PARALLEL END WALLS SPACAED APART BY SAID PERIPHERAL WALL ALONG THE LONGITUDINAL AXIS THEREOF; SAID PERIPHERAL WALL HAVING LOBE JUNCTIONS IN A ZONE CLOSER TO SAID LONGITUDINAL AXIS THAN THE REMAINDER OF SAID WALL; A DRIVE SHAFT TRANSPIERCING SAID END WALLS AND HAVING AN ECCENTRIC PORTION DISPOSED WITHIN SAID OUTER BODY, SAID ECCENTRIC PORTION HAVING AN AXIS DISPLACED FROM AND PARALLEL TO SAID OUTER BODY AXIS AND PLANETATING THEREAROUND; A MULTIAPEXED INNER BODY DISPOSED WITHIN SAID OUTER BODY AND MOUNTED ON SAID ECCENTRIC PORTION FOR ROTATION ABOUT SAID ECCENTRIC AXIS WITH SAID APEXES SWEEPING SAID INNER SURFACE IN SEALING RELATION THERETO; SAID INNER BODY HAVING AT EACH END THEREOF AND END FACE BEARING END FACE SEALS DISPOSED ADJACENT TO THE EDGES OF SAID END FACE AND GENERALLY PARALLEL THERETO, SAID END FACE SEALS SWEEPING THE INNER SURFACE OF SAID END WALLS IN SEALING RELATION THERETO; EACH OF SAID END WALLS HAVING ITS INNER SURFACE FACED WITH A HARD WEAR-RESISTANT METAL IN THE REGION OF AT LEAST ONE OF SAID LOBE JUNCTIONS AND THE REMAINDER OF THE INNER SURFACE FACED WITH A LESS WEAR-RESISTANT METAL. 